Physical activity and Alzheimer’s-related hippocampal atrophy

August 4, 2014

Physical activity may help prevent atrophy of the hippocampus, a brain region important for learning and memory that often shrinks in the brains of people with Alzheimer’s disease. A recent study that looked at the rate of atrophy over 18 months in cognitively normal older adults suggests that physical activity may help prevent or delay this Alzheimer’s-related change.

The NIA-funded study by researchers at the Cleveland Clinic’s Schey Center for Cognitive Neuroimaging is the first to show the protective effects physical activity may have on the hippocampus in older adults at genetic risk for Alzheimer’s. It also adds to past findings that physical activity, from gardening to walking to structured exercise programs, may benefit cognitive function in older adults.

Researchers studied 97 cognitively normal adults, age 65 to 89, some of whom had a family history of dementia. They were divided into four groups based on their self-reported levels of physical activity (low or high) and the presence or absence of the apolipoprotein E (APOE) ɛ4 gene form, the strongest known genetic risk factor for Alzheimer’s disease. Individuals with low physical activity said they walked or did other low-intensity activities on 2 or fewer days per week; those with high activity said they engaged in moderate or vigorous activity, such as brisk walking or swimming, on 3 or more days per week.

All participants underwent magnetic resonance imaging (MRI) of the brain to measure the size of the hippocampus—a part of the brain that shrinks as Alzheimer’s progresses—and other brain structures, as well as neurobehavioral testing to measure cognition and daily functioning. MRI scans were done at the beginning of the study and after 18 months. At the study end, researchers found the size of the hippocampus decreased by 3 percent in the group with high genetic risk and low physical activity. Hippocampal size remained stable in the group with low genetic risk and in participants with high genetic risk/high physical activity. Physical activity did not appear to affect several other brain areas, including the amygdala, thalamus, and cortical white matter.

While promising, more research is needed to confirm these findings. Researchers want to learn how physical activity influences hippocampal atrophy in people at high genetic risk of Alzheimer’s. Animal studies suggest several possibilities, including the impact of physical activity on cholinergic function, brain inflammation, and cerebral blood flow.